It has long been known from the prior art to execute moving blades and/or guide vanes of a gas turbine in a built-up or otherwise constructed blade arrangement in which the blade leaves and the upper and/or lower platforms of the blades are formed as separate components which are then assembled in the blade arrangement and sealingly connected.
A guide vane arrangement is shown in U.S. Pat. No. 5,332,360, which is incorporated by reference, shows two guide vanes, which are assembled together with an outer and an inner shroud portion and are soldered to one another along peripheral grooves. Sealing between the blades and shrouds or platforms in this case achieved by means of the soldering itself. A comparable configuration is reproduced in FIG. 1: In the blade arrangement 10 of FIG. 1, two blade leaves 11 are inserted in corresponding openings of two mutually opposite platforms or shroud segments 12 and 13. Each of the blade leaves has a leading edge 14 and a trailing edge 15. The hot gas flowing through the blade leaves 11 between the two platforms 12 and 13 flow in this case from the leading edge 14 to the trailing edge 15. A comparable arrangement is also shown in U.S. Pat. No. 5,797,725, which is incorporated by reference.
Furthermore, U.S. Pat. No. 7,052,234, which is incorporated by reference, shows, in blade arrangements, to combine ceramic blade leaves with metallic platforms or shrouds and to seal off the interspaces between the blade leaves and platforms by means of special seals. However, directed leakages of cooling air may also be used, as shown in U.S. Pat. No. 7,329,087, which is incorporated by reference, in order to prevent hot gas from penetrating into the interspaces between the ceramic blade leaves and the metallic platforms.
U.S. Patent Application Publication No. 2010/124502, which is incorporated by reference, shows to produce the blade leaf and blade platform as separate components and to assemble them, so as to decouple the two parts mechanically. In this case, too, specific seals have to be provided between the components in order avoid the penetration of hot gas.
In most cases, it is necessary, in addition to installing a simple linear sealing arrangement around the blade leaf, to purge this sealing arrangement also from the rear side with cooling air which is under a corresponding pressure higher than the pressure of the hot gas, but identical along the entire sealing arrangement. This means, in particular, that the pressure of the purging air is the same on the pressure side of the blade leaf as on the suction side, where, in fact, less pressure is required on account of the lower pressure in hot gas. This leads to a higher and needless consumption of cooling air in those regions of the blade leaf or of the sealing arrangement where a lower pressure would be sufficient. This then also applies to the leading edge and the trailing edge of the blade leaf where different pressure conditions prevail in the hot gas.